Herbicidal compositions comprising dimethenamid and a pyridazinone herbicide

ABSTRACT

Co-application of dimethenamid with pyridazinone herbicides such as norflurazon provides improved herbicidal activity.

This application is a division of application Ser. No. 08/467,367, now U.S. Pat. No. 5,721,191, filed Jun. 6, 1995, which is a continuation-in-part of application Ser. No. 08/153,946, filed Nov. 16, 1993, abandoned, which is a continuation of application Ser. No. 08/019,386, abandoned, filed Feb. 18, 1993; a continuation-in-part of application Ser. No. 08/152,066, abandoned, filed Nov. 12, 1993 which is a continuation-in-part of application Ser. No. 08/019,933, abandoned, filed Feb. 19, 1993; and a continuation of application Ser. No. 08/236,732, filed May 2, 1994.

The present invention concerns a method of controlling undesired plant growth employing co-application of dimethenamid and at least one other herbicide, herbicidal compositions comprising dimethenamid and at least one other herbicide and the use of such compositions in controlling undesired plant growth.

Dimethenamid (FRONTIER®) whose chemical name is 2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)-acetamide, processes for its production, herbicidal compositions containing it and its use as a herbicide are described in U.S. Pat. No. 4,666,502 the contents of which are incorporated herein by reference. Dimethenamid consists of 4 stereoisomers due to two chiral elements and can thus also exist in the form of the individual isomers as diastereomeric mixtures (1S, aRS (known as S-dimethenamid) and 1R, aRS (known as R-dimethenamid)) and as a racemic mixture (1RS, aRS). References herein to dimethenamid refer to its various forms unless otherwise stated. Of the diastereomeric mixtures S-dimethenamid is preferred.

The term herbicides, as used herein, refers to compounds which combat or control undesired plant growth. This class of compounds may be divided into sub-classes according to the primary type or mode of action the herbicide has on the plant. For example according to G. F. Warren of Purdue University, Indiana, U.S.A., herbicides can be classified as auxin transport inhibitors, growth regulator herbicides, photosynthesis inhibitors, pigment inhibitors, growth inhibitors, amino acid synthesis inhibitors, lipid biosynthesis inhibitors, cell wall biosynthesis inhibitors, rapid cell membrane disruptors as well as "miscellaneous" herbicides which do not come under one of the preceding categories.

It has now surprisingly been found that co-application of dimethenamid and at least one other herbicide results in better and in some cases longer-lasting control of undesired plant growth. This synergistic effect exhibits itself in a high degree of control at co-application rates which are significantly lower than the rate of each individual compound required to obtain the same degree of control. Furthermore, at any given co-application rate the degree of control is higher than the additive effect obtained for the individual components at the same rate. In some cases both speed of activity and level of control are enhanced and/or weeds can be controlled which are not controlled by either component at economical rates.

This synergistic effect allows for satisfactory control at reduced application rates for each component and even at levels which if applied for a particular component alone would give insufficient control. Additionally, longer residual control may be achieved. This provides for significant economic and environmental advantages in the use of dimethenamid and the herbicide(s) used in combination therewith.

Co-application can be achieved using tank mixes of preformulated individual active ingredients. Simultaneous or sequential (preferably 1-2 days) application of such formulations or application of preformulated fixed pre-mix combinations of the individual active ingredients.

Examples of herbicides which may be used in combination with dimethenamid in accordance with the invention include

1. auxin transport inhibitors, e.g. naptalam

2. growth regulators, including 1) benzoic acids. e.g. dicamba; b) phenoxy acids i) acetic acid type, e.g. 2,4-D, MCPA, ii) propionic acid type, e.g. 2,4-DP, MCPP, iii) butyric acid type, e.g. 2,4-DB, MCPB; c) picolinic acids and related compounds, e.g. picloram, triclopyr, fluroxypyr, clopyralid

3. photosynthesis inhibitors, including a) s-triazines i) chloro substituted, e.g. atrazine, simazine, cyanazine, ii) methoxy substituted, e.g. prometon, iii) methylthio substituted, e.g. ametryn, prometryn; b) other triazines, e.g. hexazinone, metribuzin; c) substituted ureas, e.g. diuron, fluometuron, linuron, tebuthiuron, thidiazuron, forchlorfenuron; d) uracils, e.g. bromacil, terbacil; e) others, e.g. bentazon, desmedipham, phenmedipham, propanil, pyrazon, pyridate

4. pigment inhibitors, including a) pyridazinones, e.g. norflurazon; b) isoxazolones, e.g. clomazone; c) others, e.g. armitrole, fluridone

5. growth inhibitors, including a) mitotic disruptors i) dinitroanilines, e.g. trifluralin, prodiamine, benefin, ethalfluralin, isopropalin, oryzalin, pendimethalin; ii) others, e.g. DCPA, dithiopyr, thiazopyr, pronamide; b) inhibitors of shoots of emerging seedlings i) thiocarbamates, e.g. EPTC, butylate, cycloate, molinate, pebulate, thiobencarb, triallate, vernolate; c) inhibitors of roots only of seedlings, e.g. bensulide, napropamide, siduron; d) inhibitors of roots and shoots of seedlings, including chloroacetamides e.g. alachlor, acetochlor, metolachlor, diethatyl, propachlor, butachlor, pretilachlor, metazachlor, dimethachlor, and others e.g. cinmethylin

6. amino acid synthesis inhibitors, including a) glyphosate, glufosinate; b) sulfonylureas, e.g. rimsulfuron, metsulfuron, nicosulfuron, triasulfuron, primisulfuron, bensulfuron, chlorimuron, chlorsulfuron, sulfometuron, thifensulfuron, tribenuron, ethametsulfuron, triflusulfuron, clopyrasulfuron, pyrazasulfuron, prosulfuron (CGA-152005), halosulfuron, metsulfuron-methyl, chlorimuron-ethyl; c) sulfonamides, e.g. flumetsulam (a.k.a. DE498); d) imidazolinones, e.g. imazaquin, imazamethabenz, imazapyr, imazethapyr, imazmethapyr

7. lipid biosynthesis inhibitors, including a) cyclohexanediones, e.g. sethoxydim, clethodim; b) aryloxyphenoxys, e.g. fluazifop-(P-butyl), diclofop-methyl, haloxyfop-methyl, quizalofop; c) others e.g. fenoxaprop-ethyl

8. cell wall biosynthesis inhibitors, e.g. dichlobenil, isoxaben

9. rapid cell membrane disruptors, including a) bipyridiliums, e.g. paraquat, diquat; b) diphenyl ethers, e.g. acifluorfen, fomesafen, lactofen, oxyfluorfen; c) glutamine synthetase inhibitors, e.g. glufosinate; d) others, e.g. oxadiazon

10. miscellaneous, including a) carbamates, e.g. asulam; b) nitriles, e.g. bromoxynil, ioxynil; c) hydantocidin and derivatives; d) various, e.g. paclobutrazol, ethofumesate, quinclorac (a.k.a. BAS514), difenzoquat, endothall, fosamine, DSMA, MSMA

11. Others

a) triketones and diones of the type described in the contents of each of which are incorporated herein by reference U.S. Pat. Nos. 5,336,662; 5,608,101 EP-A 338,992; EP-A 354,889; EP-A 506,907; EP-A 137,963; EP-A 186,118; EP-A 186,119; EP-A 186,120; EP-A 249,150; and EP-A 336,898. Examples of such triketones and diones are sulcotrione (MIKADO®) whose chemical designation is 2-(2-chloro-4-methanesulfonylbenzoyl)-1,3-cyclohexane dione; 2-(4-methylsulfonyloxy-2-nitrobenzoyl)-4,4,6,6-tetramethyl-1,3-cyclohexanedione; 3-(4-methylsulfonyloxy-2-nitrobenzoyl)-bicyclo 3,2,1!octane-2,4-dione 3-(4-methylsulfonyl-2-nitrobenzoyl)-bicylco 3,2,1!octane-2,4-dione; 4-(4-chloro-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)dione; 4-(4-methylthio-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)-dione; 3-(4-methylthio-2-nitrobenzoyl)-bicyclo- 3,2,1!octane-2,4-dione; 4-(2-nitro-4-trifluoromethoxybenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)-dione.

b) Compounds of the type described in U.S. Pat. No. 5,506,192 EP-A 461,079; EP-A 545,524; EP-A 315,889 and PCT Appln. No. 91/10653 the contents of which are incorporated herein by reference including for example 3- (4,6-dimethoxy-2-pyrimidinyl)hydroxymethyl!-N-methyl-2-pyridine carboxamide; 4,7-dichloro-3-(4,6-dimethoxy-2-pyrimidinyl)-3-hexanoyloxyphthalide; 3- (4,6-dimethoxy-2-pyrimidinyl)carbonyl!-N,N-dimethyl-2-pyridine carboxamide; 3,6-dichloro-2- (4,6-dimethoxy-2-pyrimidinyl)carbonyl!benzoic acid; 6-chloro-2- (4,6-dimethoxy-2-pyrimidinyl)thio!benzoic acid (a.k.a. DPX-PE350 or pyrithiobac) and salts thereof.

The present invention therefore concerns a method of combatting or controlling undesired plant growth or otherwise regulating plant growth which comprises co-applying to a locus where such combatting or control is desired an herbicidally or plant growth regulating effective aggregate amount of dimethenamid and at least one other herbicide.

Application rates for co-application will of course vary depending upon climatic conditions, season, soil ecology, weeds to be combatted and the like, however, successful results can be obtained e.g. with rates of dimethenamid of 0.1 to 3.0 kg/ha, preferably 0.1 to 2.0 kg/ha, especially 0.25 to 1.5 kg/ha e.g. 0.9 to 1.5 kg/ha in co-application with rates for partner herbicides which correspond to or are significantly lower than recommended for use thereof individually.

The suitability of specific co-applications for pre- or post-emergent uses and selectively will of course depend on the partners chosen.

The activity of dimethenamid is described in the above mentioned patents and that of suitable herbicidal partners is described in the literature or on commercially available forms thereof (cf also CROP PROTECTION CHEMICALS REFERENCE, 9th edition (1993) Chemical & Pharmaceutical Press, New York, N.Y.; The Pesticide Manual, 9th edition (1991), British Crop Protection Council, London; Ag Chem New Product Review, Ag Chem Information Services, Indianapolis, Ind.; Farm Chemicals Handbook, 1993 edition, Meister Publishing Company, Willoughby, Ohio and the like).

The invention also provides herbicidal or plant growth regulating compositions comprising an herbicidally effective aggregate amount of dimethenamid and at least one other herbicide.

Such compositions contain the active substances in association with agriculturally acceptable diluents. They may be employed in either solid or liquid forms e.g. in the form of a wettable powder or an emulsifiable concentrate, incorporating conventional diluents. Such compositions may be produced in conventional manner, e.g. by mixing the active ingredient with a diluent and optionally other formulating ingredients such as surfactants and oils.

The term diluents as used herein means any liquid or solid agriculturally acceptable material which may be added to the active constituent to provide a more easily or improved applicable form, or to achieve a usable or desirable strength of activity. Examples of diluents are talc, kaolin, diatomaceous earth, xylene, non-phytotoxic oils, or water.

Particular formulations, to be applied in spraying forms such as water dispersible concentrates or wettable powders, may contain surfactants such as wetting and dispersing agents. e.g. the condensation product of formaldehyde with naphthalene sulphonate, an alkylarylsulphonate, a lignin sulphonate, a fatty alkyl sulphate, an ethoxylated alkylphenol or an ethoxylated fatty alcohol.

In general, the formulations include from 0.01 to 90% by weight of active agent(s) and from 0 to 20% by weight of agriculturally acceptable surfactant, the active agent consisting of dimethenamid and at least one other herbicide. Concentrate forms of compositions generally contain between about 2 and 90%, preferably between about 5 and 80% by weight of active agent. Application forms of formulation may for example contain from 0.01 to 20% by weight of active agent.

When employing concurrent, immediately sequential or tank mix applications the herbicide partner(s) can be employed in commercially available form if appropriate and at rates equivalent to or preferably below those recommended by the manufacturer or in the references cited above. Dimethenamid can also be applied in commercially available form (e.g. as FRONTIER® herbicide) or as formulated e.g. as described in the above-mentioned U.S. Pat. No. 4,666,502.

On co-application according to the present invention other compounds having biological activity, e.g. compounds having insecticidal or fungicidal activity, may also be included.

The preferred mode of application is tank mix prepared e.g. by adding dimethenamid to a tank containing the other herbicide partner and an appropriate surfactant or vice versa depending on the type of herbicide partner chosen. It is advisable to consult labels of mixing partners and to conduct compatibility tests prior to mixing.

Depending on the choice of co-application partners both pre- and post-emergence activity on a large range of broadleaf and grassy weeds may be achieved. Examples of such weeds are

Agropyron repens--quackgrass

Brachiaria platyphylla--broadleaf signalgrass

Bromus spp--e.g. downybrome

Cenchrus spp.--e.g. southern sandbur, sandbur, field sandbur

Dactyloctenium aegyptium--crowfootgrass

Digitaria spp--e.g. crabgrass, smooth crabgrass, large crabgrass

Echinochloa crus-galli--barnyardgrass

Eleusine indica--goosegrass

Eriochloa spp.--e.g. southwestern cupgrass, prairie cupgrass, woolly cupgrass

Leptochloa filiformis--red spangletop

Oryza sativa--red rice

Panicum spp--e.g. witchgrass and fall-, browntop- and texas-panicum, wild proso millet

Poa annua--annual bluegrass

Setaria spp--e.g. giant foxtail, foxtail millet, yellow foxtail, bristly foxtail, green foxtail

Sorghum almum--sorghum almum

Sorghum bicolor--shattercane

Sorghum halepense--seedling johnson grass

Urochloa panicoides--liverseedgrass

Acanthospermum hispidum--bristly starbur

Amaranthus spp--e.g. pigweed, tumble pigweed; smooth pigweed, redroot pigweed, prostrate pigweed, waterhemp, spiny amaranth

Ambrosia artemisiifolia--common ragweed

Bidens pilosa--hairy beggarticks

Capsella bursa-pastoris--shepherdspurse

Chenopodium album--common lambsquarters

Cleome monophylla--spindlepod

Commelina spp--e.g. dayflower

Crotalaria sphaerocarpa--

Datura stranionium--jimsonweed

Desmodium tortuosum--Florida beggarweed

Euphorbia nutans--nodding spurge

Euphorbia maculata--spotted spurge

Galinsoga parviflora--smallflower galinsoga

Ipomea spp.--e.g. ivyleaf-, tall-, pitted morningglory

Lamium purpureum--purple deadnettle

Matricaria chamomilla--wild chamomile

Mollugo verticillata--carpetweed

Papaver rhoeas--corn poppy

Polygonum spp.--e.g. smartweed, annual smatweed, wild buckwheat, prostrate knotweed

Portulaca oleracea--common purslane

Richardia scabra--Florida pusley

Schkuhria pinnata--dwarf marigold

Sida spinosa--prickly sida

Solanum spp.--e.g. black nightshade, E. black nightshade, hairy nightshade, silverleaf nightshade

Stellaria media--common chickweed

Tagetes minuta--wild marigold (khaki weed)

Cyperus esculentis--yellow nutsedge

Cyperus iria--rice flatsedge

In addition the following weeds may also be controlled when employing appropriate mixing partners.

Abutilon theophrasti--velvetleaf

Hibiscus trionum--Venice mallow

Avena fatua--wild oats

Sinapis alba--white mustard

Xanthium strumarium--common cocklebur

Cassia obtusifolia--sicklepod

Apera spica-venti--windgrass

Campsis radicans--trumpet creeper

Rottboellia exaltata--itchgrass

Cynodon dactylon--bermudagrass

Lespedeza spp.--e.g. lespedezas

Trifolium spp.--e.g. clovers

Hippuris vulgaris--marestail

Asclepias spp.--e.g. milkweeds

Salvia spp.--lanceleaf sage

Salsola iberica--Russian thistle

Convolvulus arvensis--field bindweed

Cirsium arvense--Canada thistle

Proboscidea louisianica--devilsclaw

Senecio spp.--e.g. common groundsel

Chorispora tennela--blue mustard

Alopecurus myosuroides--blackgrass

Sisymbrium altissimum--tumble mustard

Caperionia palustris--texasweed

Crop selectivity will also usually depend upon choice of partners. Dimethenamid exhibits excellent selectivity in corn (maize), soybean and several other crops.

Examples of particular partners for co-application with dimethenamid include these selected from one or more of the types listed under a) through w) below,

a. benzoic acids, e.g. dicamba

b. picolinic acids and related compounds, e.g. picloram, triclopyr, fluroxypur, clopyralid

c. phenoxys, e.g. 2,4-D, 2,4-DB, triclopyr, MCPA, MCPP, 2,4-DP, MCPB

d. other chloracetamides, e.g. alachlor, acetochlor, metolachlor, diethatyl, propachlor, butachlor, pretilachlor, metazachlor, dimethachlor especially metolachlor, alachlor, acetochlor

e. amides, e.g. propanil, naptalam

f. carbamates, e.g. asulam

g. thiocarbamates, e.g. EPTC, butylate, cycloate, molinate, pebulate, thiobencarb, triallate, vernolate

h. nitriles. e.g. bromoxynil, ioxynil

i. ureas, e.g. diuron, thidiazuron, fluometuron, linuron, tebuthiuron, forchlorfenuron

j. triazines, e.g. atrazine, metribuzin, cyanazine, simazine, prometon, ametryn, prometryn, hexazinone

k. diphenyl ethers, e.g. acifluorfen, fomesafen, lactofen, oxyfluorfen

l. dinitroanilines, e.g. trifluralin, prodiamine, benefin, ethalfluralin, isopropalin, oxyzalin, pendimethalin

m. sulfonylureas e.g. rimsulfuron, metsulfuron, nicosulfuron, triasulfuron, primisulfuron, bensulfuron, chlorimuron, chlorsulfuron, sulfometuron, thifensulfuron, tribenuron, ethametsulfuron, triflusulfuron, clopyrasulfuron, pyrazasulfuron, prosulfuron (CGA-152005), halosulfuron, metsulfuron-methyl, chlorimuron-ethyl;

n. imidazolinones, e.g. imazaquin, imazamethabenz, imazapyr, imazethapyr, imazmethapyr

o. cyclohexanediones, e.g. sethoxydim

p. aryloxyphenoxys, e.g. fluazifop

q. bipyridiliums, e.g. paraquat, diquat

r. pyridazinones, e.g. norflurazon

s. uracils, e.g. bromacil, terbacil

t. isoxazolones, e.g. clomazone

u. various, e.g. glyphosate, glufosinate, methazole, paclobutrazol, bentazon, desmedipham, phenmedipham, pyrazon, pyridate, amitrole, fluridone, DCPA, dithiopyr, pronamide, bensulide, napropamide, siduron, flumetsulam, sethoxydim, fluazifop, clethodim, diclofop-methyl, fenoxaprop-ethyl, haloxyfop-methyl, quizalofop, diclobenil, isoxabenz, oxadiazon, paclobutrazol, ethofumesate, quinclorac, difenzoquat, entothall, fosamine, DSMA, MSMA

v. Group 11a "others" as described above.

w. Group 11b "others" as described above.

Especially preferred partners among groups a) through w) are those of groups a), m), n), u) and v), i.e. the sulfonylureas and the triketones and diones.

The co-application of the combination of dimethenamid and triketone(s) or dione(s) according to present invention is especially suitable in crops of monocotyledons, such as cereals, maize and rice. However, application in maize corps being infested with monocotyledonous and dicotyledonous weeds is most advantageous, as harmful effects against the crop plants are not enhanced. Both pre- and postemergence application to the undesired weeds is possible with this preferred combination. However, the preferred time point of application in maize is after emergence of the maize seedlings.

Application rates for co-application of dimethenamid and a triketone or dione will of course vary depending upon climatic conditions, season, soil ecology, weeds to be combatted and the like, however, successful results can be obtained, e.g. in co-application with rates of the triketone or dione which are significantly lower than recommended for use thereof alone: e.g. 0.01 to 2 kg/ha, preferably 0.1 to 1 kg/ha, especially 0.1 to 0.6 kg/ha.

From this group, combinations are preferred wherein the triketone or dione is selected from 4-(4-chloro-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5-(4H, 6H)dione, and sulcotrione, with sulcotrione being preferred.

The most preferred combination of this type is that of sulcotrione and dimethenamid. The mixture ratio will be determined according to the specific soil, crop and climate condition of use. As an example the co-application rates will be in the range of 0.9 to 1.5 kg/ha of dimethenamid and 0.15 to 0.45 kg/ha of sulcotrione. The ratio of the active ingredient in the composition by weight of sulcotrione and dimethenamid is between 1:2 and 1:10.

For the co-application in a preferred 3-way mix comprising dimethenamid and a triketone or dione of group v), the third component is preferably selected from the group j), i.e. the group of triazine herbicides. In a typical 3-way mix the triazine component will be present in a ratio of 3:1 to 1:3 relative to the dimethenamid content, with an excess of dimethenamid being preferred, i.e. a preferred ratio of 1:1 to 1:3, e.g. 1:1.5. The preferred triazine herbicide in this type of a 3-way mix is atrazine.

The co-application of the combination of dimethenamid and sulfonylurea(s) according to present invention is especially suitable in crops of monocotyledons, such as cereals, maize, sugar cane and rice. For example, application in sugar cane being infested with monocotyledonous and dicotyledonous weeds is particularly advantageous, as the harmful effects against the crop plants are not enhanced, but the weeds are controlled very effectively. Both pre- and postemergence applications to the undesired weeds is possible with this combination. However, the preferred time point of application to sugar cane is after emergence of the sugar cane seedlings, or transplantation of ratoon cane.

In this use the application rates for co-application of dimethenamid and a sulfonylurea will of course vary depending upon climatic conditions, season, soil ecology, weeds to be combatted and the like, however, successfull results can be obtained, e.g. in co-application with rates of the sufonylurea which are significantly lower than the recommended use thereof alone; e.g. 1 to 150 g/ha, preferably 10 to 100 g/ha.

From this group the preferred combination for control of weeds in sugar cane is one wherein the sulfonylurea is chlorimuron. The mixture ratio will be determinable according to the specific soil, crop and climate condition of use. As an example the co-application rates will be in the range of 0.9 to 3.0 kg/ha of dimethenamid and 10 to 100 g/ha of chlorimuron. For the combatting of cyperus spp. in sugar cane crop they may be for example 2.0 to 3.0 kg/ha of dimethenamid and 50 to 90 g/ha of chlorimuron. The ratio of active ingredient in the composition by weight of chlorimuron and dimethenamid is between 1:3000 and 1:20, preferably 1:30 to 1:60, e.g. 1:34 or 1:38 or 1:45.

For the co-application in a preferred 3-way mix comprising dimethenamid and a sulfonylurea of group m), the third component is preferably selected from the group i), i.e. the group of urea herbicides. In a typical 3-way mix the urea component will be present in a ratio of 2:1 to 1:4, relative to the dimethenamid content, with an excess of dimethenamid being preferred, i.e. a preferred ratio of 1:1 to 1:3, e.g. 1:2. The preferred urea herbicide in this type of a 3-way mix is diuron.

It will be appreciated that mixtures of dimethenamid with more than one herbicide e.g. 3-way mixes are also included within the purview of the invention.

Examples of specific mixing partners can be selected for example from the following: paraquat (e.g. as GRAMOXONE® or GRAMOXONE®EXTRA), simazine (e.g. as PRINCEP®), glyphosate (e.g. as ROUNDUP®), glufosinate (e.g. as BASTA®); (Compound Group I)

Further examples of specific mixing partners can be selected from the following: atrazine, cyanazine (e.g. as BLADEX® or together with atrazine as EXTRAZINE® or EXTRAZINE®II) terbutylazine, pendimethalin (e.g. as PROWL®), metribuzin, linuron (Compound Group II).

Further examples of specific mixing partners can be selected from the following: nicosulfuron (e.g. as ACCENT®) rimsulfuron (e.g. as TITUS®) and primisulfuron (e.g. as BEACON®) (Compound Group III).

Further examples of specific mixing partners can be selected from the following: imazethapyr (e.g. as PURSUIT®), imazaquin (e.g. as SCEPTER®), chloramben, aclonifen (Compound Group IV).

Further examples of specific mixing partners can be selected from the following: dicamba (e.g. as BANVEL®, as CLARITY® (in DGA salt form) or together with atrazine as MARKSMAN®).

Further examples of specific mixing partners can be selected from sethoxydim (e.g. as POAST®), fluazifop (e.g. as FUSILADE®) (Compound Group V).

Further examples of specific mixing partners can be selected from the following: sulcotrione (e.g. as MIKADO®) and 4-(4-chloro-2-nitro-benzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5-(4H,6H) dione (Compound Group VI).

Further examples of specific mixing partners for 3-way mix are sulcotrione (e.g. as MIKADO®) and atrazine (e.g. as GESAPRIM®) (Compound Group VIa).

Further examples of specific mixing partners include chlorimuron (e.g. as CLASSIC® or in a 3-way mix together with diuron as FRONT®) (Compound Group VII).

According to the desired weed spectrum, time of application and the like other specific herbicides listed within the groups a) through w) above are also particular examples of suitable mixing partners.

It has now also been found that very efficient control of grassy weeds in crops of sugar cane can also be with herbicides of the class of chloracetamides in co-application with at least one herbicide of the class of sulfonylurea herbicides (group m) optionally in the presence of at least one herbicide of the class of the urea herbicide (group i). These components synergistically enhance the herbicidal effect of the mixture. The chloroacetamides are widely used in agricultural practice. Preferred species of this group are inter alia Alachlor (LASSO®) whose chemical designation is 2-chloro-2',6'-diethyl-N-methoxymethyl-acetanilide; Acetochlor (HARNESS®) whose chemical designation is 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide; Metolachlor (DUAL®) whose chemical designation is 2-chloro-6'-ethyl-N-(2-methoxy-1-methylethyl)-aceto-toluidide; Metazachlor (BUTISAN S®) whose chemical designation is 2-chloro-N-(pyrazol-1-yl-methyl)acet-2',6'-xylidide; and dimethenamid (FRONTIER®) whose chemical designation is 2-chloro-N(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)-acetamide.

Application rates of chloroacetamides for co-application will of course vary depending upon climatic conditions, season, soil ecology, weeds to be combatted and the like, however, successful results in sugar cane can be obtained e.g. with rates of the chloroacetamide of 1 to 6 kg/ha, preferable 2 to 5.5 kg/ha in co-application with sulfonylurea and urea herbicides. For example the specific application rates of the chloroacetamide component is 3 to 6 kg/ha for Alachlor, e.g. 5.9 kg/ha, and 3 to 5 kg/ha for Metolachlor, e.g. 4.3 kg/ha.

The mixture ratio of the chloroacetamide herbicide with the sulfonylurea is generally between 20:1 and 300:1, preferably 20:1 to 100:1, e.g. 30:1 or 90:1. When a urea herbicide is co-applied with the mixture of a chloroacetamide and a sulfonylurea it may preferably be applied in a ratio of 1:1 to 1:5, relative to the chloroacetamide, e.g. 1:2 or 1:3 or 1:4. The preferred chloroacetamides other than dimethenamid to be applied in sugar cane with chlorimuron and diuron are acetochlor or metolachlor.

Thus, another aspect of present invention is the control of grassy weeds in sugar cane with a combination of a chloroacetamide in association with a sulfonylurea and an urea herbicide. Specific preferred combinations for this use are mixtures of dimethenamid, acetochlor, alachlor or metolachlor with a combination of chlorimuron and diuron, e.g. in the commercially available 1:19 mixture FRONT®.

EXAMPLE 1

Active ingredients are weighed and dissolved in a stock solution consisting of acetone:deionized water, 1:1, and 0.5% adjuvant mixture consisting of surfactants SPAN® 20:TWEEN® 20:TWEEN® 85, 1:1:1. Dilutions from this stock solution are performed to allow for preparation of spray solutions consisting of single doses of individual or combined active ingredients. Each dose is applied simultaneously via a linear track sprayer set to deliver 600 liters/ha spray volume to both the foliage of the selected weed seedling species, postemergence application, and the surface of soil that had been previously sown with seeds, preemergence application. The seedlings used are cultured to develop plants at the two- to early three-leaf stage. The stage of development of each seedling at application time is recorded. After application, the treated plants are transferred to the greenhouse and held until termination of the experiment within four weeks. Symptoms of injury are recorded two and ten days after postemergence application and fourteen days after preemergence application. Visual percentage ratings of crop injury and weed control are taken ten and twenty-eight days after postemergence application and fourteen and twenty-eight days after preemergence application.

Co-application of dimethenamid with other specific active ingredients such as outlined above produces improved herbicidal effects compared with application of each active ingredient alone.

EXAMPLE 2

A field trial is carried out employing dimethenamid (as FRONTIER® 7.5 EC) and nicosulfuron (as ACCENT® 75 WDG) in control of large crabgrass in corn. Application is as tankmix combination at early post-emergence of the weeds (3 and 4 leaf stages). Application rates of a.i. are 1.5 and 0.75 kg/ha for dimethenamid and 37.2 and 19.2 g/ha for nicosulfuron. Combined application of 0.75 kg/ha of dimethenamid and 19.2 g/ha of nicosulfuron gave 85% control with negligible corn damage compared with 35% for nicosulfuron applied alone at 19.2 g/ha and 72% for dimethenamid at a higher rate of 1.25 kg/ha. Combined application at the higher rate of dimethenamid with 37.2 g/ha of nicosulfuron gave an even more dramatic effect with 95% control compared with 72% for dimethenamid and only 45% for nicosulfuron each alone.

Similar effects are noticed on combined treatment of broadleaf weeds such as lambsquarters, prickly sida and morningglory employing 1.12 kg/ha of dimethenamid (as FRONTIER®) and 0.071 kg/ha of imazethapyr (as PURSUIT®).

EXAMPLE 3

Small field units in a maize field, infested with Echinochloa crus galli and Solanum nigrum are sprayed with a tank-mix suspension of dimethenamid and sulcotrione. The stage of the weeds is "full tillering" for Echinochloa crus galli and "8-leaves stage" for Solanum nigrum. The lot size is 8 meters in length and 3 meters in width. The application rates are 1.1 kg/ha of dimethenamid and 0.15 kg/ha of sulcotrione. Seven days after treatment the efficacy is evaluated, both as control of the weeds and as tolerance of the crop plants.

In this test the control of echinochloa was between 93 and 98%, and the control of solanum was between 91 and 93% in three repetitions, while the damage of the maize plants was always below 10%.

EXAMPLE 4

Small field units in a maize field, infested with Echinochloa crus galli, Solanum nigrum and Chenopodium album are sprayed with a tank-mix suspension of dimethenamid, sulcotrione and atrazine. The stage of the weeds is "full tillering" for echinochloa and "6-8 leaves stage" for solanum and chenopodium. The lot size is 8 meters in length and 3 meters in broadth. The application rates are 1.08 kg/ha of dimethenamid, 105 or 210 g/ha of sulcotrione and 750 g/ha of atrazine. 14 days after treatment the efficacy is evaluated. The results (in percentage control) were as follows:

    ______________________________________                            expected                             additive                                     synergistic     Compound a.i./ha       effect   effect     ______________________________________                       Echino-                       chloa                       control     Atrazine 1500     23        --     Dimethenamid/Atrazine 1080/750                       30       --     Sulcotrione/Atrazine 150/750                       26       --     Sulcotrione/Atrazine 210/750                       33       --     Dimethenamid/Sulcotrione/Atrazine                       95       56       +39     1080/150/750     Dimethenamid/Sulcotrione/Atrazine                       97       59       +42     1080/210/750                       Solanum/                       Cheno-                       podium     Atrazine 1500     16       --     Dimethenamid/Atrazine 1080/750                       36       --     Sulcotrione/Atrazine 150/750                       23       --     Sulcotrione/Atrazine 210/750                       53       --     Dimethenamid/Sulcotrione/                       97       53       +44     Atrazine 1080/150/750     Dimethenamid/Sulcotrione/                       100      89       +11     Atrazine 1080/210/750     ______________________________________

The synergistic effect is clearly visible at the lower rates of sulcotrione, resulting in a nearly doubled degree of control, compared to the expected additive efficacies. For the higher rates of sulcotrione, (>300 g/ha) only the additive effect remains visible since the total control is 100%.

EXAMPLE 5

A field trial is carried out on plots (2×20 m) planted with sugar cane and infested with Cyperus rotundus in the first or second growing stage and sprayed with a backpack sprayer in different concentrations in a tank mix. The amount of liquid spray broth is 400 l/ha. The application rates are 2.7 kg/ha of dimethenamid with 60 g/ha of chlorimuron or with 1.6 kg/ha of a fixed ratio mixture of chlorimuron and diuron (1:19) which is commercially available as FRONT®. Visual evaluation is done 30 or 60 days after treatment (DAT) in percentage of control. The expected additive effect value is calculated according to the method of Colby:

    ______________________________________                                expected     Compound a.i./ha                    Cyperus     additive synergistic     conditions     Control (DAT)                                effect   effect     ______________________________________     light to medium soil     Dimethenamid 2.7 kg                    19 (60 DAT) --     Chlorimuron/Diuron                    45 (60 DAT) --     1.6 kg     Dimethenamid/Chlorimuron/                    76 (60 DAT) 55       +21     Diuron 2.7 + 1.6 kg     heavy soil     Dimethenamid 2.7 kg                    10 (60 DAT) --     Chlorimuron/Diuron 1.6                    37 (60 DAT) --     kg     Dimethenamid/Chlorimuron/                    74 (60 DAT) 43       +31     Diuron 2.7 + 1.6 kg     light to medium soil     Dimethenamid 2.25 kg                    23 (30 DAT) --     Chlorimuron/Diuron 1.2                    48 (30 DAT) --     kg     Dimethenamid/Chlorimuron/                    80 (30 DAT) 60       +20     Diuron 2.25 + 1.2 kg     light to medium soil     Dimethenamid 2.7 kg                    27 (30 DAT) --     Chlorimuron/Diuron 1.2                    48 (30 DAT) --     kg     Dimethenamid/Chlorimuron/                    88 (30 DAT) 62       +26     Diuron 2.7 + 1.2 kg     light to medium soil     Dimethenamid 2.7 kg                    27 (30 DAT) --     Chlorimuron 0.06 kg                    58 (30 DAT) --     Dimethenamid/Chlorimuron                    93 (30 DAT) 69       +24     2.7 + 0.06 kg     ______________________________________

The achieved results indicate that synergistic effects are obtained with the 2-way mix (dimethenamid/chlorimuron), as well as with the 3-way mix (dimethenamid/chlorimuron/diuron).

EXAMPLE 6

In the procedure as set out in Example 5, tank mixtures of 5.7 kg/ha of alachlor or 4.3 kg/ha of metolachlor with 1.2 kg/ha of the fixed ratio mixture of chlorimuron and diuron (1:19; commercial FRONT®) where applied to a sugar cane field. The results were as follows:

    ______________________________________     Compound a.i./ha                   Cyperus    expected   synergistic     conditions    Control (DAT)                              additive effect                                         effect     ______________________________________     light to medium soil     Alachlor 5.4 kg                   30 (30 DAT)                              --     Chlorimuron/Diuron 1.2                   48 (30 DAT)                              --     kg     Alachlor/Chlorimuron/                   85 (30 DAT)                              64         +21     Diuron 5.4 + 1.2 kg     light to medium soil     Metolachlor 4.3 kg                   23 (30 DAT)                              --     Chlorimuron/Diuron 1.2                   48 (30 DAT)                              --     kg     Metolachlor/Chlorimuron/                   89 (30 DAT)                              60         +29     Diuron 4.3 + 1.2 kg     ______________________________________

The achieved results indicate that synergistic effects are obtained with the tested 3-way mixtures. 

What is claimed is:
 1. A herbicidal composition comprising a herbicidally effective amount of dimethenamid, a pyridazinone herbicide, and an agriculturally acceptable carrier.
 2. The composition of claim 1 wherein the amount of dimethenamid is such that it can be applied at a rate from 0.1 to 3.0 kg/ha.
 3. The composition of claim 1 wherein the amount of dimethenamid is such that it can be applied at a rate from 0.25 to 1.5 kg/ha.
 4. The composition of claim 1 wherein the amount of the pyridazinone herbicide is such that it can be applied at a rate from 0.1 to 3.0 kg/ha.
 5. A method of controlling undesired plant growth in the presence of a crop comprising applying postemergence to the locus of said undesired plant growth, a herbicidally effective aggregate amount of dimethenamid and a pyridazinone herbicide wherein the application rate of dimethenamid is from 0.1 to 3.0 kg/ha.
 6. The method of claim 5 wherein the application rate of the pyridazinone herbicide is from 0.1 to 3.0 kg/ha.
 7. The method of claim 5, wherein the application rate of dimethenamid is from 0.25 to 1.5 kg/ha.
 8. The method of claim 5 wherein the crop is maize.
 9. The method of claim 5 wherein the undesired plant growth to be controlled is a grassy weed.
 10. The method of claim 5 wherein the undesired plant growth to be controlled is a broadleaf weed.
 11. The method of claim 5 wherein said applying step comprises co-applying dimethenamid and the pyridazinone herbicide in a tank mix.
 12. The method of claim 5 wherein said applying step comprises applying the herbicides simultaneously to the locus of said undesired plant growth.
 13. The method of claim 5 wherein said applying step comprises applying the herbicides sequentially to the locus of said undesired plant growth.
 14. A method of controlling undesired plant growth in the presence of a maize crop comprising applying postemergence to the locus of said undesired plant growth a herbicidally effective aggregate amount of dimethenamid and a pyridazinone herbicide wherein the dimethenamid and pyridazinone herbicide are applied either simultaneously or in sequential application. 